The history of the Byzantine Empire merges with the history of the original Roman Empire which it grew out of. But although there was never a day when the eastern half of the empire announced that it was now a different entity, the story of the Greek speaking Byzantines is radically different from that of their Latin predecessors.

Nowhere is this clearer than in military strategy. The early history of the Romans was about domination. They aimed to destroy their enemies. Caesar summed it up in a few words. 'I came, I saw, I conquered.' The Romans aspired to be and soon became the predominant military power in their world by the simple process of eliminating all their rivals.

But once that power collapsed, what was left was a new world full of aggressors who were certainly dangerous, but none of which were strong enough themselves to replace Rome as the overwhelming superpower.

As a former military policy wonk in the Pentagon, Edward Luttwak would probably describe this as a move from a unipolar to a multi-polar world, or something like that. Luckily for the reader he doesn't bring much of the jargon from his day job to his account of the strategic problems facing the Byzantines. But he does bring the insight of someone who has wrestled with those kinds of dilemmas. He is not afraid to be controversial. In fact he seems to relish it. I heard him on the radio in the UK recently astonishing an interviewer with the view that the US should withdraw its troops from Afghanistan and instead bribe the Chinese to occupy it. Whatever the pros and cons of this approach, at the very least it would be cheaper. And given that foreign policies rarely have the desired outcome picking one that requires a low outlay of blood and treasure deserves to at least be considered. So that impressed me enough to seek out this book.

This isn't Luttwak's first study of Roman history. He has also famously written a book about the western empire's defensive strategy, which I have yet to read. This got a mixed reception with many specialists not agreeing with it. But this book covering the Grand Strategy of the Byzantine Empire has received as far as I can tell universally positive write ups and doesn't seem to contradict the conventional wisdom. It is certainly a good read. You don't need any prior knowledge to follow it and the author doesn't make too many references to other works in the field, so even though it is detailed and scholarly it is perfectly suitable for a general reader even one who doesn't know anything about the subject. He does use a few unfamiliar terms that you might need to look up. To give one example and to save you the trouble, redacting gets used quite a lot. It means editing together a document from multiple sources. I imagine that is an everyday word in an intelligence gathering department but not for those of us who don't work with spies regularly. But it reminds you that Luttwak is a backroom guy and this a book about what was happening in the backrooms of Constantinople during centuries it was the centre of a declining empire trying, always against the odds but usually successfully, to survive in a hostile world.

There was a culture in Constantinople that individual emperors could draw on, and contribute to. The Byzantines studied war as a science and wrote up what they learned. This gave them an edge that allowed them to deal with their many enemies in the field effectively. The goal was not the glory of an individual commander. Alexander the Great would have got short shrift. They did not aim to eliminate the enemy. Pitched battles with their inevitable losses of precious troops were to be avoided. Clever strategies and spying were the preferred way to operate. Professional soldiers require training, equipping and supplying - all resource intensive procedures. The result was highly effective troops, but there were never many of them and they could not easily be replaced.

The perennial shortage of manpower meant that military investment was capital intensive. Weapons were sophisticated with designs committed to vellum and later to paper. Some forms dated back to antiquity others were more recent innovations. The most famous was the Greek fire that enabled attacking fleets to be completely destroyed. For all their social conservatism and deep seated religiosity the Byzantines were always ready to develop creative solutions when new problems arose.

This was never more evident than in the Byzantine response to the Huns. The Huns deployed advanced bows whose range and power combined with superb horsemanship made them invincible. They could simply fire their bows from a safe distance and massacre their enemies. If attacked they could retreat more quickly than any pursuit. Their speed allowed them to run rings around the movements of any regular army deployed against them.

For a while the Huns had the empire at their mercy. No quick countermeasures could be devised. But when the Hun menace disappeared following the death of Attila there was time for the lessons to be absorbed and used. The training of cavalry was overhauled. Bows were upgraded. Before long the Romans could deploy units as effective as the Huns themselves, but with all the machinery of a sophisticated state to back them up. This was one of the reasons that in the Sixth Century Justinian was able to revive Roman power and start the reconquest of much that had been lost. He even recaptured Rome itself. If he could have matched the numbers as well as the skills of the Huns, who knows what he might have achieved.

But even when it was at its strongest the Byzantine position was always fragile. The state could only function thanks to highly efficient tax collection. But this in turn created a concentration of highly visible and portable wealth that made it everyone's target of choice. It was never strong enough to overawe everyone at the same time. It was necessary to project what is now called soft power as well. Byzantine officials underwent huge journeys, thousands of miles sometimes, to influence foreign powers and get them to do their bidding using guile, gold and God. The religious prestige of the emperor and the archbishop of Constantinople could be used to help achieve state objectives. Subsidies, gifts and out and out bribery were also in the toolkit, as was intrigue. Dissidents who might be useful were always welcome.

Byzantine commanders didn't just follow the book without any imagination. They often formulated highly creative and risky solutions to the problems they faced. For example once sending a large force into the Persian homeland even when the Persians were laying siege to Constantinople itself. The Byzantines were able to behave like a superpower long after they ceased to have the resources of a superpower. When they were at war they used the forces at their disposal intelligently for maximum impact. They rarely aimed to destroy their enemies. In Byzantine diplomacy today's enemy could be tomorrow's ally. There were in any case an unlimited number of new enemies to take the place of someone you defeated, so overall final victory was never a possibility. War was never their favoured approach even though they continually prepared for it.

The Byzantine empire was finally ended in 1453 some eleven hundred years since Constantine moved the capital from Rome. For most of that time it had looked weak, often catastrophically so. It had been on its knees many times. Somehow it always managed to come through against the odds. Edward Luttwak's book goes a long way to explain how it managed it. If you are managing a declining superpower, this is a must read book.